Antenna systems used in commercial Ku Band Satellite Communication (SatCom) systems, such as Direct Broadcast Satellite (DBS) systems, and the like, must have a low profile and high radiation efficiency due to the “figure of merit” or system G/T (i.e., the ratio of the system gain (“G”) to the system noise temperature (“T”)) requirements. Moreover, antenna aperture size is directly related to radome swept volume constraints. A low profile antenna allows a maximum antenna aperture size for a given radome swept volume, maximizing the system gain (“G”) of the figure of merit or system G/T. High radiation efficiency further maximizes the gain (“G”) of the system G/T. In Ku Band SatCom antenna applications such as, for example, aircraft horizontal stabilizer (“tail”) mount antenna systems, optimizing the gain (“G”) for a limited sized antenna is critical so that an appropriate system G/T value may be realized.
Commercial Ku Band Satellite Communication (SatCom) systems employ satellites that transmit and receive signals in a rotating corkscrew-like pattern. This mode of transmission, referred to as circular polarization allows the antenna to rotate to an arbitrary angle without being placed in a cross-polarized state. In this way, circular polarization reduces or eliminates the possibility of polarization miss-match, which can cause a reduction in the data rate. Waveguide antennas capable of radiating circularly polarized fields typically employ a rectangular waveguide having radiation apertures consisting of pairs of slots cut in the broad wall of the waveguide. These slots are positioned at 90 degrees to each other so that they cross at their centers to form an X-shaped opening in the waveguide which functions as a circularly polarized radiating element. However, such radiation apertures do not account for the intrinsic shape of the internal H-field within the fundamental TE10 rectangular waveguide mode limiting the efficiency of the waveguide antenna.
Accordingly, it would be desirable to provide an improved low-profile, low-loss dual polarization waveguide antenna having an array of waveguide slot pairs that are configured for receiving and/or radiating a circularly polarized (CP) field, and which account for the intrinsic shape of the internal H-field within the fundamental TE10 rectangular waveguide mode. It is further desirable that the slots of the waveguide slot pairs be arranged to provide control over the sense of the circularly polarized (CP) radiated field, and for allowing the antenna to receive both left-hand and right-hand circularly polarized fields (LHCP and RHCP).